116 M. Brochant OM i^e 



might be named schistose felspathic talc or chlorite^ or, iu 

 order not to depart too much from the names under which 

 many of its varieties have been noticed, talcose (or chlorite) 

 felspathic schist. The following is its geological association. 

 It is known how abundant talc and talcose rocks are in 

 the Alps ; the mica slates which are there also frequently 

 found, and in the same associations, afford continual pas- 

 sages of mica into talc, from mica slate to talcose slate, and 

 even into the green schist named chlorite schist (chlorite 

 schistoide). It may even be said that talc, and the talcose 

 rocks in general, are much more frequently met with than 

 mica and the micaceous rocks. The micaceous limestones 

 are much more rare than the talcose limestones ; and this 

 predominance of talc is above all greater on the Italian side, 

 although it is also observed on the other side of the chain. 



Almost all the micaceous or talcose schists are green, and 

 of a green analogous to that of chlorite. Distinct plates of 

 mica or talc are rarely seen in it ; it presents more or less 

 shining surfaces, having frequently a slightly fibrous texture. 

 Among these rocks, to which one would be inclined to 

 give solely the generic name of talcose schists^ since the 

 greater part are really talcose, and the passage of talc into 

 mica is so frequently seen in the same block ; there are 

 some mixed with crystals of felspar, which are the com- 

 pound rocks, that I name, as I have already said, talcose 

 felspathic schists. 



They are very frequent in the Alps ; I have observed 

 them in Savoy, the Valais, the valley of Aosta, and in 

 numerous places ; they are most abundant in the environs of 

 Mont Cervin ; and I have since found them in rocks from 

 Corsica. It is impossible that these talcose felspathic schists 

 should have escaped the attention of the numerous geolo- 

 gists who have visited these countries ; yet it does not ap- 

 pear that they are often found in collections ; neither have 

 they been separately noticed in geological descriptions of 

 different formations, nor in the classifications of rocks ; 

 they have no doubt been partly comprised in the gneiss, 

 partly in the mica slates, and partly in the chlorite slates. 



